Personal audio devices have been used with increasing regularity in recent years, and a greater number of people are using headphones as part of their daily activities. Consequently, engineering headphone devices has become a robust and specialized field requiring advanced technologies to meet the design, aesthetic, and functional requirements of the various users of these devices. Headphones come in a variety of shapes and sizes. One type of headphone device includes two small speakers held within two separate enclosures that are meant to fit or rest directly within a user's ear. These headphone devices are commonly called earphones or earbuds. Because the anatomy of each person's ear is unique, however, earbuds that are mass produced do not always provide an adequate fit for each unique user's individual ear anatomy. For users with small ears, an earbud that fits too tightly within the ear canal can cause discomfort during use. In some instances, the inadequacy of the fit renders the earbuds entirely unusable.
Though some have attempted to remedy this problem by providing cushions in multiple sizes (e.g. typically two to three different sizes—small, medium, large—may be provided), the fit remains inadequate for those having inner ear canal dimensions much smaller than average. This entails nearly 10% of users.
Finding an adequate remedy to this problem is complicated by the structural limitations and performance requirements of certain earbud devices.
Structurally, an earbud generally has a plastic or metal housing that encloses several electronics, including at the very least a speaker component and appropriate wiring. Advanced earbud devices can include BLUETOOTH wireless connectivity, and thus require the earbud housing to enclose additional electronic components (e.g. a battery, a circuit board, an amplifier, a channel equalizer, a wired or wireless receiver, or other audio-electronic circuitry). Earbud devices typically have a tip extending outward from the remainder of the housing, upon which a silicone or foam cushion may be attached. Thus, the size of the cushions used with a particular set of earbuds is necessarily limited by the size of the tip. Accordingly, for user's with small ears, decreasing the overall diameter or thickness dimension of the earbud tip is essential to enabling the use of sufficiently small earbud cushions.
With respect to performance, the capacity of the electronics within an earbud are limited by their size. For instance, a speaker functions by pushing and pulling air molecules to generate pockets of high and low pressure that the human eardrum is capable of detecting, and that the human brain is capable of interpreting as sound. As the size of speaker parts (e.g. voice coil, spider, cone, magnet) decrease, so does the speaker's capacity to push and pull air molecules to generate sound. In other words, smaller speakers generate less volume and produce narrower frequency ranges than larger speakers. To some degree, the lower capacity of small speakers can be alleviated by bringing the speaker in close proximity to the user's eardrum. The closer the speaker is to a user's eardrum, the easier it is for the human eardrum to detect the pressure fluctuations. Moreover, the closer the speaker is to the user's eardrum, the less noise exists that can interfere with the already small pressure fluctuations. Thus, an optimal earbud design includes a speaker component that is situated at or near the tip of the earbud—the part actually inserted into the user's ear canal.
Accordingly, a problem exists. In particular, making an earbud tip small enough to accommodate very small ear canal's would require—in presently earbud models—moving the speaker component out of the earbud tip and into the remainder of the earbud housing so that the tip size can be reduced. But moving the speaker component into the remainder of the housing moves speaker parts further from the user's eardrum, thereby reducing the overall sound quality as described above. What's more, moving the speaker into the housing means less space for the other components disposed within the housing. This can be particularly problematic for wireless earbuds—which also house batteries, receivers, channel equalizers, and other components—where space within the housing is already limited. For instance, further congesting the earbud housing space with the speaker component might mean having to reduce the size of the battery, which would reduce the time a person can use the earbuds on a single charge.
This dilemma makes it challenging to design earphones that provide an adequate fit for users having small ear canal dimensions, but still maintain the sound quality and other advantages (described above) that come from situating the speaker component at the tip of the earbud device.